| Bifidobacteria are probiotic organisms that improve the microbial balance in the human gut and can be added as live cultures to fermented dairy foods for consumption. However, bifidobacteria are susceptible to the low pH of fermented dairy products.; The primary objective of the study was to investigate the effect of microencapsulation on the viability of bifidobacteria in set and stirred plain yogurt during refrigerated storage for 30 days. Changes in the profile of organic acids in plain, set and stirred yogurt containing bifidobacteria were also determined during fermentation and refrigerated storage. Finally, the effect of freezing and hardening on the integrity of microcapsules containing bifidobacteria in yogurt was also studied.; Cell enumeration, titratable acidity, pH, and consumer sensory analysis were carried out for the yogurt samples. Ion-exchange high-performance liquid chromatography was done for quantification of organic acids. SEM was employed to study the microcapsules in yogurt and frozen yogurt.; Microbiological results for set yogurt showed a decline of 78.0% and 70.5% in the population of Bifidobacterium longum B6 and B. longum ATCC 15708, respectively, for the treatments containing non-encapsulated cells. The decline was 89.3% and 91.8%, respectively, in stirred yogurt. No change was observed in bifidobacterial population of set and stirred yogurts containing encapsulated bifidobacteria.; Concentrations of acetic and lactic acids increased during storage, while those of citric and uric acids remained the same for all the treatments. No pattern was observed for concentrations of propionic or butyric acid, while the content of pyruvic acid initially decreased and then increased during storage. The higher acetic acid content in set yogurt containing non-encapsulated bifidobacteria indicated metabolic activity of bifidobacteria during storage.; Consumers judged the set yogurt containing non-encapsulated bifidobacteria as most sour. Yogurt containing encapsulated bifidobacteria was liked the least. In stirred yogurt, no difference was observed between control (without bifidobacteria) and yogurt containing encapsulated bifidobacteria in the consumer acceptability test, although the texture of the latter was perceived as grainy.; Cryo-field emission scanning electron microscopy revealed that the integrity of the microcapsules in the frozen yogurt was not disrupted by either the dynamic action of the freezer mutator or by freezing and hardening.; It can be concluded that microencapsulation increases the viability of bifidobacteria in yogurt. This technique can be used to transmit bifidobacteria via fermented products provided that sensory characteristics of the product are improved. |
